Surface mount packages are a well known means of constructing electronic circuits where components are mounted directly to circuit boards. Many types of surface mount packages are known, including dual in-line packages, quad in-line packages and grid arrays.
As integrated circuit technology shrinks, the need arises for smaller and denser mechanical interfaces between the integrated circuits and the circuit boards on which they are mounted. Dual in-line, quad in-line and to grid arrays reflect the natural progression in increased density. However, with greater density comes a greater number of points of potential failure. Grid arrays are perhaps the most problematic when it comes to detecting failures, as the actual failure can occur within the array, between the integrated circuit and the circuit board, making detection (let alone repair) of the fault nearly impossible. These and other drawbacks of grid arrays, particularly ball grid arrays, are discussed at http://nepp.nasa.gov/index_nasa.cfm/773 “Ball Grid Array (BGA) and http://nepp.nasa.gov/index_nasa.cfm/777, “Recommendations for BGA/CSP Qualification and Flight Implementation” as published by NASA Electronic Parts and Packaging Program (NEPP).
CALTEX Scientific, 192-T Technology Dr., Irvine, Calif. 92618 USA sells various products such as BGA Scope BH-1000 system for inspection and measurement of BGA and Micro BGA. The BGA Scope BH-1000 is essentially a high-resolution camera connected to a computer-monitor that can be used to navigate within the BGA to visually inspect each ball for defects. Unfortunately, this type of system is extremely complex and requires some degree of access to the integrated circuit in order to orient the camera so as to be able to perform the inspection.
A still further known way to detect failures in BGAs can be found in Lizheng Zhang, I. Charles Ume, Juergen Gamalski and Klaus-Peter Galuschki, 2006, Detection of Flip Chip Solder Joint Cracks Using Correlation Coefficient and Auto-Comparison Analyses of Laser Ultrasound Signals, IEEE Transactions on Components and Packaging Technologies, vol. 29, No. 1, p. 13-19. (“Zhang”) Again, however, Zhang requires complex equipment and skill in order to detect failures in a BGA.